U.S. Pat. No. 5,300,068 granted to Rosar et al. discloses an electrosurgical apparatus for cutting tissues and for ablating vascular occlusions. Rosar discloses a guide wire that includes a flexible wire with an electrically insulating coating over sections of the wire. The end portion of the wire is received in a bore of an electrically and thermally insulating tip. The distal end of the wire is substantially flush with the distal end of the tip. The distal end of the wire exposed at the distal end of the tip forms an electrode. However, Rosar et al. do not disclose an electrode that is formed/positioned distal to the electrically and thermally insulating tip. The electrode of Rosar is surrounded by the electrically and thermally insulating tip. Furthermore, the electrode of Rosar has a diameter that is less than the outer diameter of the tip. Rosar et al. do not teach an electrode having a diameter that is at least equal to that of the device distal end. Thus, the apparatus of Rosar et al. does not provide an electrode for creating a channel in tissue that can allow the device distal end to be advanced without hindrance through the tissue. Additionally Rosar et al. do not disclose an electrode distal to the insulating tip that secures the tip and allows the tip to be held in place.
U.S. Pat. No. 5,230,349 granted to Langberg discloses an electrical heating catheter having an active electrode that is partially covered by a heat conducting and electrically insulating heat-sink layer for localizing and controlling an electrical heating of tissue and cooling of the active electrode by convective blood flow. The cooling provided by the heat-sink layer increases the depth and volume of an ablation region. Langberg discloses an active electrode designed for electrical heating of tissue for ablation. However, Langberg does not teach an electrode tip operable to create a channel through tissue. Additionally, Langberg discloses a heat-sink layer that functions to increase the depth and volume of ablation. However, Langberg does not teach a thermal shield for protecting the insulated portion of the catheter.